Effects of phosphorus on growth, biochemical parameters and intestinal microbiota of the juvenile hybrid of Acipenser baerii ♀×Acipenser schrenckii ♂

Phosphorus (P) plays a vital role in fish life and its application in aquatic feed deserves thoroughly study. To evaluate the effects of dietary P on growth performance, serum biochemical parameters and intestinal microbiota of the juvenile hybrid of A. baerii♀ × A. schrenckii♂, five diets containing 3.7, 6.5, 9.6, 12.2 and 14.8 g/kg of available phosphorus (AP) were assigned to feed fish at initial weight of 10.06 ± 0.39 g for 8 weeks. The results showed that weight gain (WG) of juvenile hybrid sturgeon was improved significantly with dietary AP level up to 9.6 g/kg. Feed efficiency (FE) and P digestibility of fish were significantly enhanced by P supplementation, but were dropped when dietary AP level further increased to 12.2 and 14.8 g/kg. Alkaline phosphatase (ALP) activity increased firstly and then slightly decreased at a stable level in the high dietary AP groups (12.2 and 14.8 g/kg). With dietary AP level increasing, significantly decrease of the content of triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) in serum were observed. Serum antioxidant indicators including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and total antioxidant capacity (T-AOC) exhibited the improved activity by addition P in diet. Intestinal microbiota analysis indicated that the supplementation of P in diet increased the richness and diversity of bacteria communities. Cyanobacteria was the dominant phyla in the intestine of hybrid sturgeon, and was significantly increased in P addition group. Compared with the basal diet group, abundant genera in dietary P supplementation group exhibited a higher diversity and were composed of Clostridium, Cetobacterium, Bacteroides, Empedobacter, Ruminococcus, Faecalibacterium, Rhodococcus and Candidatus Arthromitus. In conclusion, appropriate dietary P supplementation could positively affect the growth, biological processes and intestinal microbial communities of fish, and a level of 8.5 g/kg of AP in diet is suggested for juvenile hybrid sturgeon.